Navigation involves, among other things, the solution of vector triangles and the determination of a direction, a rate of travel, and the distance between two points for a moving object. These determinations must be repeated for each change of course heading, present position, current set and drift, and/or wind direction. Even for a short trip, the calculations can become voluminous. The labor needed for accurate piloting of a vessel has been reduced significantly by the use of mechanical aids which facilitate the drawing of the directional course line, maintaining reference lines to read the true heading directly from a compass rose scale, and providing fixed scales for mathematical computations.
Unfortunately, most navigational aids are limited in the functions they provide. Some solve only time, speed, and distance problems for a single vessel on a given course, and they are not capable of performing the calculations necessary to avoid or intersect a moving object. Examples of such devices are shown in U.S. Pat. Nos. 2,027,368; 2,280,485; 3,203,101; 3,231,188; 3,361,346; 3,625,417; and 3,862,398. Many such aids require an auxilliary chart or map upon which the vector plots must be drawn, such as in U.S. Pat. Nos. 1,113,717; 1,984,390; 3,059,339; 3,379,493; 3,496,640; 3,540,127; 3,643,333; and 3,881,253. Only a few devices offer an associated plotting surface upon which to draw course vectors lines, and when a plotting surface is provided, the scales and drawing area are small and require an additional surface onto which the plot may extend. Examples of such devices having a plotting surface are found in U.S. Pat. Nos. 1,984,390 and 3,540,127. All devices which use either auxilliary maps and charts or additional surfaces on which to extend the plotted vectors require the extrapolation of data from the plotting surface and separate interpolation onto a compass rose to obtain the proper course heading and speed. This makes navigation cumbersome, difficult, and inaccurate. Bearing these deficiencies in mind, the unique advantages of the present invention will become apparent.